Research On Wire And Arc Additive Manufacturing Technology And Microstructure Performance Of Die Material RMD545

RMD545 is a wear-resistant surfacing flux-cored wire,which is suitable for the overall additive manufacturing of medium and small hammer forging dies of 5CrNiMo,H13 and other materials and the repair and manufacturing of the bottom of the cavity of the large-scale forging die.But there is no systematic research work on this welding wire.This article proposes to use the GMA-AM method to conduct an in-depth study on the forming process,cladding thermal process and organizational performance of RMD545 additive manufacturing,provide a theoretical basis for the additive repair of die steel,and promote the practical application of metal material arc additive manufacturing.Firstly,an arc additive manufacturing test system is established,and a single-layer single-pass welding test is carried out.The effect of welding current and stacking speed on the quality of the welding forming is studied.The test shows that the metal cooling speed is fast at a small welding current of 100?140A,and the welding path is prone to serious hump phenomenon.At a medium welding current of 150?200A,the welding path is well formed.In the good forming interval,the influence of process parameters on the forming size of the deposit is studied.The results show that the deposit current and the deposition speed have a significant effect on the deposit width.Comparing the microstructures of the cladding channels under different cladding currents,as the cladding current increases,the metal cooling rate decreases,the Martensitic transformation variable decreases,and the bainite transformation variable increases.The finite element software is used to numerically simulate the thermal process of multi-layer single-pass cladding.The study of the temperature field shows that with the increase of the number of cladding layers,the heat dissipation conditions of the formed parts becomes worse,the heat accumulation is serious,and the area of the hightemperature area gradually increases.By extracting the midpoint thermal cycle curve of the deposited layer,it is found that the latter layer has a heating remelting effect on the previous layer,and as the number of deposited layers increases,the peak temperature of the midpoint thermal cycle curve of the deposited layer gradually decreases.The T_8/5 and T_8/3 in the thermal cycle curve of the midpoint of the cladding layer gradually increase with the increase of the number of cladding layers,which further illustrates that the heat accumulation phenomenon in the cladding process of the forming part gradually increases,and the metal structure of the cladding layer The change has an impact.Finally,on the basis of the previous work,a welding current of 160 A and a deposition speed of 5mm/s are selected for multi-layer single-pass welding test.The surface of the formed part is good without obvious defects.The thermal process of the deposited metal at different locations is different.The structure from bottom to top is: tempered martensite + acicular ferrite + a small amount of bainite,martensite + bainite + a small amount of acicular ferrite body,lath martensite.The hardness of the shaped parts is between 350 and 500 HV,corresponding to the structure distribution.The yield strength,tensile strength and elongation are 995 MPa,1197 MPa,and 18.8%.They show the characteristics of ductile fracture and meet the performance requirements of mold repair.